What was noticeable all over Warsaw were the overfilled garbage cans and litter in the streets that nobody cleaned up.

noticeable 是由动词 notice（注意到）加上形容词后缀 -able（能够...的）构成，意思是"显而易见的、引人注目的"。-able 后缀表示"具有某种特性或能力"，所以 noticeable 指"容易被注意到的"。